Ophthalmologic imaging apparatuses for photographing subject's eyes are known from the past. An ophthalmologic imaging apparatus includes, for example, an illumination optical system that projects an illumination light beam onto a subject's eye and an imaging optical system that guides reflection light from the fundus to an imaging device. Some of such ophthalmologic imaging apparatuses have an autofocus function that changes the focus position of the imaging optical system by projecting two split indicators onto the fundus of the subject's eye and moving the focus lens based on the positional relationship between two split indicator images acquired by the returning light from the fundus.
In an ophthalmologic imaging apparatus with the autofocus function, a focusable range by the movement of the focus lens is set to be a range in which diopter of an average subject's eye is correctable. Accordingly, there are cases in which the focus position of the imaging optical system cannot be determined even when the focus lens is moved with respect to a subject's eye with high myopia or with high hyperopia. Therefore, in order to enable performing focus adjustment for subject's eyes with high myopia or with high hyperopia with the focus lens, a diopter correction lens is inserted into the optical path of the imaging optical system.
However, when the diopter correction lens has been inserted into the optical path of the imaging optical system, the optical relationship between the imaging optical system and the focus optical system that projects the split indicators onto the fundus changes, and the split indicator images cannot be acquired by the imaging optical system. As a result, not only automatic focusing by the autofocus function but also manual focusing using the split indicators becomes impossible.
For example, Patent Document 1 proposes a technique in which manual focusing can be smoothly performed in a state where the diopter correction lens has been inserted into the optical path by moving the focus lens in such a way that a moving speed for the case where the diopter correction lens has been inserted into the optical path is faster than a moving speed for the case where the diopter correction lens has been removed.
Japanese Unexamined Patent Application Publication No. 2011-189063
However, in the ophthalmologic imaging apparatus disclosed in Patent Document 1, focus adjustment cannot be performed automatically when the diopter correction lens has been inserted into the optical path of the imaging optical system. This requires long time for those who are unfamiliar with the apparatus to perform adjustment of the focus position, and it becomes difficult to perform focusing with high precision.